Steep the tea you are using for the tea jello in hot water for the recommended time. For example, if you are using a black tea, steep it in freshly boiled water for 4-5 minutes. If you are using a green tea, steep it in under boiling water for 2-3 minutes. Remove and discard the tea bags or strain the loose leaf tea after steeping.
In a small saucepan, add the steeped tea, sugar and agar agar powder. Whisk to combine.
Place the small saucepan over high-heat and bring the mixture to a boil, whisking often to ensure that the agar agar powder has fully dissolved. Reduce heat to a low boil for 5 minutes, whisking often again.
Remove the saucepan from the heat and carefully pour the tea jello mixture into molds, heat-proof containers or individual serving cups. Refrigerate for at least 2 hours until firm.
Remove from molds or cut into cubes if you used a container instead. Serve on its own or garnish with whipped cream, fresh fruit and/or herbs. Tea jello should be served chilled. Keep any leftovers in an airtight container in the fridge for up to 2 days.